From most concrete silos or the like concrete containers, especially such ones used in connection with concrete molding machines, each time dispensing of concrete takes place a specified amount of concrete, only slightly varying from time to time, has to be given off. As closing mechanisms for such silos or containers are most commonly used manually or automatically operated slide gates. Such a slide gate may be operated with a relatively close accuracy, especially when the concrete is relatively wet and, consequently, more free-flowing. Very often, however, a concrete is used containing only relatively small amounts of water and, therefore, having a very low viscosity, and such a concrete has shown when flowing through pipes or openings of limited dimensions to have a marked tendency to pack along the pipe walls or along the periphery of the opening and, besides, shortly after an outlet having been opened and after some, normally irregular, lumps of concrete having fallen out the concrete has a tendency of forming a plug-like assembly domed upwards at its lower end. Such a concrete assembly or concrete plug may be loosened by gentle knock or by the use of an agitator within the container, but even in such cases the concrete will have a tendency of falling out as lumps whereby an accurate dosing and an even distribution of the concrete within a mold may be made difficult, especially in case the distribution is performed by means of a swivelling distribution chute.
For conveying of concrete it is known to use a single threaded worm conveyor having, however, a very great power consumption even when used for downwards vertical transport and in spite thereof that in this case the weight of the concrete should facilitate the transport. Besides, such worm conveyors also bring about a relatively uneven transport of the concrete. Therefore, even if such a worm conveyor, provided it was arranged within the outlet of a concrete silo or other concrete container, could possibly be effective as a closing mechanism, hitherto such worm conveyors have never been used for said purpose, and when vertically arranged they have been used within concrete containers they have only served as conveying agitators.